Image Processing Apparatus and Image Processing Method That Ensure Improved Visibility of Character After Conversion into Monochrome Image Data, and Recording Medium Therefor

ABSTRACT

An image processing apparatus includes an image-data acquiring unit, a character recognition processing unit, and a monochrome conversion unit. The image-data acquiring unit acquires image data representing an image including a character. The character recognition processing unit performs a character recognition process on the image data to extract a character region. The character region is a region where the character is represented. The monochrome conversion unit converts the image data into monochrome image data when the image data is color image data including a color image. The monochrome image data includes a monochrome image representing the color image with a single color. When a tone difference between the extracted character region and an adjacent region is smaller than a predetermined threshold, the monochrome conversion unit changes a tone of a boundary region between the character region and the adjacent region adjacent to the character region.

INCORPORATION BY REFERENCE

This application is based upon, and claims the benefit of priority from,corresponding Japanese Patent Application No. 2016-120305 filed in theJapan Patent Office on Jun. 16, 2016, the entire contents of which areincorporated herein by reference.

BACKGROUND

Unless otherwise indicated herein, the description in this section isnot prior art to the claims in this application and is not admitted tobe prior art by inclusion in this section.

A typical image forming apparatus reads a color image on an originaldocument to print not only the color image but also a monochrome image,which is preferred in terms of cost reduction. When the monochrome imageis printed from the color image on the original document, color imagedata is converted into monochrome image data. The conversion into themonochrome image data converts RGB information (R: red, G: green, B:blue) into single-color-grayscale information. This causes informationon hue and saturation to be lost. Thus, when a print density differencebetween adjacent regions is small, it is difficult to distinguish aboundary between the adjacent regions in the printed image.

On the other hand, visibility of a printed matter after the monochromeconversion is different for each user, and the users have respectivepreferences. Thus, the obtained printed matter may be a printed matterdifferent from an image intended by the user. To solve such problem, forexample, there is proposed a technique that performs a preview displayof a plurality of pieces of alternative image data having differentprint densities of two adjacent regions in a monochrome image on anoperation panel to enable the user to select the alternative image data.

SUMMARY

An image processing apparatus according to one aspect of the disclosureincludes an image-data acquiring unit, a character recognitionprocessing unit, and a monochrome conversion unit. The image-dataacquiring unit acquires image data representing an image including acharacter. The character recognition processing unit performs acharacter recognition process on the image data to extract a characterregion. The character region is a region where the character isrepresented. The monochrome conversion unit converts the image data intomonochrome image data when the image data is color image data includinga color image. The monochrome image data includes a monochrome imagerepresenting the color image with a single color. When a tone differencebetween the extracted character region and an adjacent region is smallerthan a predetermined threshold, the monochrome conversion unit changes atone of a boundary region between the character region and the adjacentregion. The adjacent region is a region adjacent to the characterregion.

These as well as other aspects, advantages, and alternatives will becomeapparent to those of ordinary skill in the art by reading the followingdetailed description with reference where appropriate to theaccompanying drawings. Further, it should be understood that thedescription provided in this summary section and elsewhere in thisdocument is intended to illustrate the claimed subject matter by way ofexample and not by way of limitation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a block diagram illustrating a functionalconfiguration of an image forming system according to one embodiment ofthe disclosure.

FIG. 2 illustrates contents of a monochrome conversion process accordingto the one embodiment.

FIG. 3 illustrates contents of an edge highlight process according tothe one embodiment.

FIG. 4 illustrates contents of a first and a second edging processesaccording to the one embodiment.

FIG. 5 illustrates contents of a third and a fourth edging processesaccording to the one embodiment.

FIG. 6 illustrates a result of an edging process according to acomparative example.

DETAILED DESCRIPTION

Example apparatuses are described herein. Other example embodiments orfeatures may further be utilized, and other changes may be made, withoutdeparting from the spirit or scope of the subject matter presentedherein. In the following detailed description, reference is made to theaccompanying drawings, which form a part thereof.

The example embodiments described herein are not meant to be limiting.It will be readily understood that the aspects of the presentdisclosure, as generally described herein, and illustrated in thedrawings, can be arranged, substituted, combined, separated, anddesigned in a wide variety of different configurations, all of which areexplicitly contemplated herein.

The following describes a configuration for implementing the disclosure(hereinafter referred to as “embodiment”) with reference to thedrawings.

FIG. 1 illustrates a block diagram illustrating a functionalconfiguration of an image forming system 1 according to one embodimentof the disclosure. The image forming system 1 includes an image formingapparatus 100 and a personal computer 200. The image forming apparatus100 includes a control unit 110, an image reading unit 120, an imageforming unit 130, a storage unit 140, a communication interface unit150, an automatic document feeder (ADF) 160, and an operation display170. The control unit 110 includes an image analysis unit 111, amonochrome conversion unit 112, and a character recognition processingunit 113.

The image forming apparatus 100 is connected to the personal computer200 using the communication interface unit 150. The personal computer200 also functions as the image analysis unit 111 and the monochromeconversion unit 112, which are included in the control unit 110. Theimage forming apparatus 100 forms an image based on the image datareceived from the personal computer 200.

The control unit 110 includes a main storage unit, such as a RAM and aROM, and a control unit, such as a micro-processing unit (MPU) and acentral processing unit (CPU). The control unit 110 has a controllerfunction related to an interface, such as various I/Os, a universalserial bus (USB), a bus, and another hardware, and controls the entireimage forming apparatus 100.

The storage unit 140 is a storage device constituted of a hard diskdrive, a flash memory, or a similar medium, which are non-transitoryrecording media, and stores control programs and data for processesperformed by the control unit 110. The storage unit 140 further storesan adjacent-coloring-print-density-difference table 141 storingthresholds.

The operation display 170 functions as a touch panel to display variousmenus as an entry screen. Further, the operation display 170 accepts anoperation input by a user from various kinds of buttons and switches(not illustrated).

FIG. 2 illustrates contents of a monochrome conversion process accordingto the one embodiment. The monochrome conversion process of theembodiment is a process that converts color image data into monochromeimage data while preventing a reduced visibility of a character.

At Step S10, the image reading unit 120 performs a scanning process. Thescanning process is a process that reads an original document using theADF 160 or a platen (not illustrated). In this example, the imagereading unit 120 and the ADF 160 (or the platen) function as animage-data acquiring unit that acquires image data. The acquisition ofthe image data is performed as, for example, also a reception of a printjob from the personal computer 200.

At Step S20, the image analysis unit 111 determines that the originaldocument is a color document or a monochrome document so as to generatecolor image data or monochrome image data based on the result of thisdetermination.

When the original document is determined to be a color document, thecontrol unit 110 advances the process to Step S30. When the originaldocument is determined to be a monochrome document, the control unit 110advances the process to Step S60. At Step S60, the image forming unit130 forms an image on a print medium based on the image data.

At Step S30, the monochrome conversion unit 112 performs the monochromeconversion process. The monochrome conversion process is a process thatconverts the color image data into monochrome image data. The colorimage data includes respective tone values of RGB. The monochrome imagedata represents a color image with a single color and is grayscale imagedata having a single tone value. The monochrome image data does notinclude information on hue and saturation. The monochrome conversionprocess ensures the calculation from the respective tone values of RGBusing, for example, a National Television System Committee (NTSC)weighted-average method.

For example, the following calculating formula achieves the NTSCweighted average method. The NTSC weighted average method is also amethod of calculating a luminance value.

Y=(0.298912×R+0.586611×G+0.114478×B)

At Step S40, the control unit 110 determines whether to perform an edgehighlight process or not. The edge highlight process is a process thatimproves the visibility of a contour in an image region representing acharacter. The determination whether to perform the edge highlightprocess or not is performed by, for example, inquiring of the user onthe operation display 170. The image forming apparatus 100 may beconfigured such that the user is inquired, for example, when theoriginal document is determined as a color document and monochromeprinting is designated.

FIG. 3 illustrates contents of the edge highlight process (Step S50)according to the one embodiment. At Step S51, the character recognitionprocessing unit 113 performs a character extraction process. Thecharacter extraction process may be performed based on theabove-described monochrome image, or may be performed based on the colorimage data. The character recognition process based on the color imagedata may be performed using color information, or may be performed aftermonochrome binarization using shading information.

In the character extraction process by character recognition, adifference between a character and a non-character is apparent in thecase of a black-and-white document, and also a character string ishorizontal writing or vertical writing. This facilitates the extraction.However, in the color document, a character string may include adecoration, such as a frame, a shade, and solid shading. Thus, it is noteasy to extract a character string body. Furthermore, the characterstring may be illustrated with gradations other than a single color. Forsuch problem, in the embodiment, at least one of a method that utilizesthe character string illustrated with a single color and a method thatextracts a region having an identical line width through a morphologicaloperation is employed as a character extraction process method using thecolor information.

At Step S52, the character recognition processing unit 113 determinespresence/absence of an adjacent colored region based on the color imagedata. The adjacent colored region is an adjacent region that is a regionadjacent to a character region representing the extracted character, andis a colored region, that is, a non-white region. When the adjacentregion, which is a region adjacent to the character region, is white, itis determined that the visibility of the character is fair.

When the adjacent colored region is determined to be absent, thevisibility of the character is fair, and thus the process is advanced toStep S60 (see FIG. 2) without performing the edging process. When theadjacent colored region is determined to be present, the process isadvanced to Step S53.

At Step S53, the monochrome conversion unit 112 determines whether aprint density difference between the character region and the adjacentcolored region is smaller than the threshold or not based on themonochrome image data. That is because a small print density differencebetween the character region and the adjacent colored region may bringreduced visibility of the character due to the character buried in itsperipheral area. Step S53 is a process for determining whether thevisibility of the character is sufficient after the monochromeconversion or not. The threshold is a tone value (tone difference) readfrom the adjacent-coloring-print-density-difference table 141 (seeFIG. 1) preliminarily stored in the storage unit 140.

When the print density difference between the character region and theadjacent colored region is determined to be equal to or more than thethreshold, the process is advanced to Step S60 (see FIG. 2) withoutperforming the edging process because of sufficient visibility of thecharacter. When the print density difference between the characterregion and the adjacent colored region is determined to be smaller thanthe threshold, the process is advanced to Step S54.

At Step S54, the monochrome conversion unit 112 determines whether theadjacent colored region is single or not based on the color image data.A single adjacent colored region means that a tone of the whole of theadjacent colored region contacting respective characters or one ofstrokes constituting the respective characters is single. A non-singleadjacent colored region means that the tone of the adjacent coloredregion contacting the respective characters or the respective strokes isnot single, that is, a plurality of adjacent colored regions havingdifferent tones are present.

When the adjacent colored region is determined to be single, the processis advanced to Step S55. When the adjacent colored region is determinednot to be single, the process is advanced to Step S56. When a pluralityof adjacent colored regions are present, and when a print densitydifference between at least one of the plurality of adjacent coloredregions and the character region is smaller than the threshold at StepS53, the process is advanced to Step S54.

At Step S55, the monochrome conversion unit 112 inquires of the userwhether to maintain line thickness of the character or not on theoperation display 170. The monochrome conversion unit 112 displays apreview image on which the edge highlight process has been performed onthe operation display 170 to enable the user to input “a selectionwhether to maintain the line thickness of the character or not” and “awidth of a white pixel for edging.” In the embodiment, the white pixelis a pixel on which toners are not formed.

When the operation display 170 receives a reply for maintaining the linethickness of the character, the monochrome conversion unit 112 advancesthe process to Step S57 a. When the operation display 170 receives areply for not maintaining the line thickness of the character, themonochrome conversion unit 112 advances the process to Step S57 b.

FIG. 4 illustrates contents of a first and a second edging processesaccording to the one embodiment. A color image region M11 is one examplewhere a part of the color image represented by the color image data isextracted. The color image region M11 includes a character region T11and an adjacent colored region S11 around the character region T11. Amonochrome image region M12 is a monochrome image represented by themonochrome image data, which is generated from the color image data bythe monochrome conversion. The monochrome image region M12 includes acharacter region T12 and an adjacent colored region S12 around thecharacter region T12.

In the color image region M11, assume that at least one difference ofhue and saturation of the character region T11 and the adjacent coloredregion S11 ensures the visibility of the character represented by thecharacter region T11. On the other hand, in the monochrome image regionM12, reduced visibility of the character represented by the characterregion T11 due to, commonly, missing both information on the hue and thesaturation of the character region T11 and the adjacent colored regionS11 is assumed.

At Step S57 a, the monochrome conversion unit 112 performs the firstedging process. The first edging process is a process that performs anedging process on a whole outside of a contour while maintaining theline thickness of the character. This edging process is a process thatconverts pixels contacting an outside of a contour of the characterregion T12 in the adjacent colored region S12 of the monochrome imageregion M12 into white pixels having a predetermined width (a distancefrom the contour) to form an adjacent colored region S12 a including awhite pixel region E12 a. This enables the monochrome conversion unit112 to generate a monochrome image region M12 a. The monochrome imageregion M12 a is an image where a peripheral area of the contour of thecharacter region T12 is converted into the white pixels having thepredetermined width. Thus, the image has improved visibility of thecharacter represented by the character region T12.

At Step S57 b, the monochrome conversion unit 112 performs the secondedging process. The second edging process is a process that performs anedging process on a whole inside of the contour without maintaining theline thickness of the character. This edging process is a process thatconverts pixels contacting an inside of the contour of the characterregion T12 in the character region T12 of the monochrome image regionM12 into white pixels having a predetermined width to form a characterregion T12 b surrounded by a white pixel region E12 b. This enables themonochrome conversion unit 112 to generate a monochrome image region M12b. The monochrome image region M12 b is an image where the inside of thecontour of the character region T12 is converted into the white pixelshaving the predetermined width. Thus, the image has improved visibilityof the character represented by the character region T12 b.

FIG. 5 illustrates contents of a third and a fourth edging processesaccording to the one embodiment. FIG. 5 illustrates one example of theedging process performed when the tone of the adjacent colored region isnot single, that is, a plurality of adjacent colored regions havingdifferent tones are present (determine at Step S54).

In this example, a color image region M21 includes a character regionT21 and two adjacent colored regions S211 and S212 around the characterregion T21. A monochrome image region M22 includes a character regionT22 and two adjacent colored regions S221 and S222 around the characterregion T22. On the adjacent colored region S221 side, a print densitydifference between the adjacent colored region S221 and the characterregion T22 is smaller than the threshold. On the adjacent colored regionS222 side, a print density difference between the adjacent coloredregion S222 and the character region T22 is equal to or less than thethreshold.

At Step S56, similarly to Step S55, the monochrome conversion unit 112inquires of the user whether to maintain the line thickness of thecharacter or not on the operation display 170. When the operationdisplay 170 receives a reply for maintaining the line thickness of thecharacter, the monochrome conversion unit 112 advances the process toStep S58 a. When the operation display 170 receives a reply for notmaintaining the line thickness of the character, the monochromeconversion unit 112 advances the process to Step S58 b.

At Step S58 a, the monochrome conversion unit 112 performs the thirdedging process. The third edging process is an edging process that ispartially performed while maintaining the line thickness of thecharacter. This edging process is a process that converts pixelscontacting an outside of a contour of the character region T22 in theadjacent colored region S221 of the monochrome image region M22 intowhite pixels having a predetermined width to form an adjacent coloredregion S221 a including a white pixel region E22 a. This enables themonochrome conversion unit 112 to generate a monochrome image region M22a. The monochrome image region M22 a is an image where a peripheral areaof the contour of the character region T22 in the adjacent coloredregion S221 a is converted into the white pixels having thepredetermined width. Thus, the image has improved visibility of thecharacter represented by the character region T22.

At Step S58 b, the monochrome conversion unit 112 performs the fourthedging process. The fourth edging process is an edging process that ispartially performed without maintaining the line thickness of thecharacter. This edging process is a process that converts all pixelsconstituting the character region T22 in the region surrounded by theadjacent colored region S221 of the monochrome image region M22 intowhite pixels to form a white pixel region E22 b. This enables themonochrome conversion unit 112 to generate a monochrome image region M22b. The monochrome image region M22 b is an image where all the pixelsconstituting the character region T22 in the region surrounded by theadjacent colored region S221 are converted into the white pixels. Thus,the image has improved visibility of the character represented by acharacter region T22 b.

In the embodiment, in Step S58 b, the character region T22 is notconverted into the white pixels having the predetermined width in theregion surrounded by the adjacent colored region S221 but all the pixelsconstituting the character region T22 are converted into the whitepixels. Such process is performed because the white pixels having apredetermined width form a region T22 ce that partially narrows acharacter width of a character region T22 c as a monochrome image regionM22 c illustrated in FIG. 6, and this brings a poor appearance. On theother hand, when all the pixels constituting the character region T22are converted into the white pixels, a character width of the characterregion T22 b is uniformly maintained while its color is inverted. Thisbrings a good appearance.

In the adjacent colored region S222 of the monochrome image region M22,the visibility of the character represented by the character region T22is ensured, and thus the edging process is not performed.

Thus, in the image forming system 1 according to the embodiment, theconversion into the monochrome image data having the improved visibilityof the character is achieved.

In addition to the above-described respective embodiments, the followingmodifications implement the disclosure.

Modification 1

While in the above-described embodiment the disclosure is applied to theimage forming apparatus 100, the disclosure may be applied to a devicethat functions as an image processing apparatus, such as an imagereading apparatus (scanner) or the personal computer 200. Specifically,the personal computer 200 performs the above-described processes forprinting the color image in monochrome with the personal computer 200,and then a print job including the already-processed monochrome imagedata may be transmitted to the image forming apparatus 100 in order toprint.

Modification 2

While in the above-described embodiment the white pixels have a limitedpredetermined width when the pixels contacting the outside of thecontour of the character region are converted into the white pixels, aprocess where all the pixels constituting the adjacent colored regionoutside the contour are converted into the white pixels may be employed.

Modification 3

While in the above-described embodiment the pixels positioned outside orinside the contour of the character region are converted into the whitepixels, for example, pixels in a region across the contour may beconverted into the white pixels. A region across the outside of thecontour of the character region, the inside of the contour of thecharacter region, and the contour is also referred to as a boundaryregion between the character region and the adjacent region.Furthermore, the pixels do not always need to be converted into thewhite pixels, and a process that the pixels are changed to have apredetermined tone value (for example, a black pixel or a light graypixel) may be employed.

Modification 4

While in the above-described embodiment the operation display and adisplay (not illustrated) of the computer enable a user to input “theselection whether to maintain the line thickness of the character ornot” and “the width of the white pixel for edging,” the operationdisplay and the display may display a toner amount saved by the whitepixels formed by the edging process. This causes the user to recognizethat the disclosure is effective to save toners also to help the usage,so as to promote the saving of the toners.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments will be apparent to those skilled in the art.The various aspects and embodiments disclosed herein are for purposes ofillustration and are not intended to be limiting, with the true scopeand spirit being indicated by the following claims.

What is claimed is:
 1. An image processing apparatus comprising: animage-data acquiring unit that acquires image data representing an imageincluding a character; a character recognition processing unit thatperforms a character recognition process on the image data to extract acharacter region, the character region being a region where thecharacter is represented; and a monochrome conversion unit that convertsthe image data into monochrome image data when the image data is colorimage data including a color image, the monochrome image data includinga monochrome image representing the color image with a single color;wherein when a tone difference between the extracted character regionand an adjacent region is smaller than a predetermined threshold, themonochrome conversion unit changes a tone of a boundary region betweenthe character region and the adjacent region, the adjacent region beinga region adjacent to the character region.
 2. The image processingapparatus according to claim 1, wherein the monochrome conversion unitconverts pixels in the boundary region into white pixels representingthe pixels in white.
 3. The image processing apparatus according toclaim 1, wherein the monochrome conversion unit positions the boundaryregion on the adjacent region side.
 4. The image processing apparatusaccording to claim 1, wherein the monochrome conversion unit positionsthe boundary region on the character region side.
 5. The imageprocessing apparatus according to claim 1, further comprising: anoperation display that displays the monochrome image having changedtones of the boundary region; wherein the operation display accepts aninput indicating whether to change the tone of the boundary region ornot.
 6. An image forming apparatus comprising: the image processingapparatus according to claim 1; and an image forming unit that forms animage on a print medium based on the monochrome image data processed bythe image processing apparatus.
 7. An image processing methodcomprising: acquiring image data representing an image including acharacter; performing a character recognition process on the image datato extract a character region, the character region being a region wherethe character is represented; and converting the image data intomonochrome image data when the image data is color image data includinga color image, the monochrome image data including a monochrome imagerepresenting the color image with a single color; wherein when a tonedifference between the extracted character region and an adjacent regionis smaller than a predetermined threshold, the converting includeschanging a tone of a boundary region between the character region andthe adjacent region, the adjacent region being a region adjacent to thecharacter region.
 8. A non-transitory computer-readable recording mediumstoring an image processing program to control an image processingapparatus, the image processing program causing the image processingapparatus to function as: an image-data acquiring unit that acquiresimage data representing an image including a character; a characterrecognition processing unit that performs a character recognitionprocess on the image data to extract a character region, the characterregion being a region where the character is represented; and amonochrome conversion unit that converts the image data into monochromeimage data when the image data is color image data including a colorimage, the monochrome image data including a monochrome imagerepresenting the color image with a single color; wherein when a tonedifference between the extracted character region and an adjacent regionis smaller than a predetermined threshold, the monochrome conversionunit changes a tone of a boundary region between the character regionand the adjacent region, the adjacent region being a region adjacent tothe character region.